[PATCH v4 2/6] KVM: arm64: Add support for FEAT_HDBSS

[Tian Zheng]

Armv9.5 introduces the Hardware Dirty Bit State Structure (HDBSS)
feature, indicated by ID_AA64MMFR1_EL1.HAFDBS == 0b0100.

Add CPU capability detection for HDBSS. The feature requires VHE mode
and is detected via ID_AA64MMFR1_EL1.HAFDBS.HDBSS field. A helper
function system_supports_hdbss() is provided to check hardware support.

Suggested-by: Zhou Wang <wangzhou1@xxxxxxxxxxxxx>
Co-developed-by: Eillon <yezhenyu2@xxxxxxxxxx>
Signed-off-by: Eillon <yezhenyu2@xxxxxxxxxx>
Signed-off-by: Tian Zheng <zhengtian10@xxxxxxxxxx>
---
 arch/arm64/include/asm/cpufeature.h |  5 +++++
 arch/arm64/kernel/cpufeature.c      | 12 ++++++++++++
 arch/arm64/tools/cpucaps            |  1 +
 3 files changed, 18 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index a57870fa96db..bdfab086fd94 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -863,6 +863,11 @@ static inline bool system_supports_haft(void)
 	return cpus_have_final_cap(ARM64_HAFT);
 }

+static inline bool system_supports_hdbss(void)
+{
+	return cpus_have_final_cap(ARM64_HAS_HDBSS);
+}
+
 static __always_inline bool system_supports_mpam(void)
 {
 	return alternative_has_cap_unlikely(ARM64_MPAM);
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 9a22df0c5120..aa327eebaf1c 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -2131,6 +2131,11 @@ static bool hvhe_possible(const struct arm64_cpu_capabilities *entry,
 	return arm64_test_sw_feature_override(ARM64_SW_FEATURE_OVERRIDE_HVHE);
 }

+static bool has_vhe_hdbss(const struct arm64_cpu_capabilities *entry, int cope)
+{
+	return is_kernel_in_hyp_mode() && has_cpuid_feature(entry, cope);
+}
+
 bool cpu_supports_bbml2_noabort(void)
 {
 	/*
@@ -2781,6 +2786,13 @@ static const struct arm64_cpu_capabilities arm64_features[] = {
 		ARM64_CPUID_FIELDS(ID_AA64MMFR1_EL1, HAFDBS, HAFT)
 	},
 #endif
+	{
+		.desc = "Hardware Dirty state tracking structure (HDBSS)",
+		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
+		.capability = ARM64_HAS_HDBSS,
+		.matches = has_vhe_hdbss,
+		ARM64_CPUID_FIELDS(ID_AA64MMFR1_EL1, HAFDBS, HDBSS)
+	},
 	{
 		.desc = "CRC32 instructions",
 		.capability = ARM64_HAS_CRC32,
diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 9b85a84f6fd4..a87706c9d160 100644
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -69,6 +69,7 @@ HAS_VA52
 HAS_VIRT_HOST_EXTN
 HAS_WFXT
 HAS_XNX
+HAS_HDBSS
 HAFT
 HW_DBM
 KVM_HVHE
--
2.33.0